The present invention relates to a tensioning device which is used to select and impart a moment of torque to an attached member such as a shaft, and which will bias the attached member to maintain contact between the attached member and a second member. The present torsional tensioning device has been found to be particularly useful in connection with conveyor belt cleaners which utilize scraper blades to clean the belt. Conveyor belt scraper blades are conventionally mounted on a shaft which is transverse to the direction of conveyor belt travel and are rotated into contact with the belt to scrape off adherent material. Over time the scraper blades wear down and lose contact with the belt thereby hampering the blades cleaning ability. The shaft on which the scraper blades are mounted must then be rotated to reposition the scraper blades against the belt.
Conveyor belt scraper blades are subjected to repeated impact forces which are generated by the blades coming into contact with conveyor belt splices and enlarged pieces of the conveyed material or debris which adhere to the belt, all of which can cause appreciable damage to the scraper blades or the conveyor mechanism. To promote effective cleaning of the conveyor belt and to avoid shutting the belt down for repair, it is of the utmost importance to provide the scraper blades with a shock absorbing capability.
Previous torsional tensioning devices of the type shown in U.S. Pat. No. 4,533,036 have been used in connection with conveyor belt scraper blades. Because of their construction, they have extended a substantial distance from the conveyor chute wall and have obstructed adjacent walkways, which on most conveyor installations are compact and have a minimum amount of clearance. Prior devices also required the use of special wrenches and did not allow for infinite settings of torque as opposing holes needed to be matched up for the insertion of connecting pins. In those devices utilizing connecting pins, the situation is often encountered where the torque that can be applied with just one hand is not quite enough to match up the opposing holes thereby requiring the use of both hands on the wrench to achieve the next hole to line up with the pin hole. This results in a second person being needed to insert the connecting pin. Prior devices also rigidly coupled the torsional device to the shaft of the cleaner blades making it likely that if the shaft should become bent, the bending force would be transmitted through the torsional device and to the person imparting the torque to the torsional sleeve. Prior devices also required rigid members inside or outside of the torsional sleeve to provide support to prevent the buckling or collapse of the torsional sleeve. Flexible couplings used in connection with shafts are shown in U.S. Pat. Nos. 2,867,102 and 2,867,103. Torsional springs are shown in U.S. Pat. Nos. 3,674,131; 4,171,920; and 4,533,036.